Williston — New Genera of Permian Reptiles. 577 



Chamasavrus dolichognathus gen. sp. nov. 



Although the type and only known specimen of the present 

 genns consists of the left mandible, lacking its posterior end, 

 the characters it presents are so peculiar that they will justify 

 its description. 



The specimen was accidentally discovered in the matrix of 

 dark reddish brown sandstone enclosing a type specimen of 

 Limnoscelis, from the Permian or Permo-Carboniferous of 

 New Mexico. The type specimen is No. 827 of the Yale 

 Museum collections. The mandible (tig. 2) is especially note- 



Fig. 2. 



Fig. 2. Left mandible of Chamasaurus dolichognathus. Twice natural 

 size. No. 827, Yale University. 



worthy because of its slenderness. That it does not belong to 

 an amphibian is evident from the teeth, which are closely set, 

 flattened, and thecodont or protothecodont, characters unknown 

 among the amphibians. The slight but distinct rugosities of 

 the mandible are cotylosaurian rather than pelycosaurian, 

 though this character is not unknown among the zygocrotaph- 

 ous reptiles. Twenty-five teeth are preserved, the most of 

 them perfectly. The tirst four or five, the sixteenth and the 

 twenty-third are injured on their outer sides, but show for the 

 most part their shapes. In front of these teeth there are alve- 

 olar emarginations for two more, which have been represented 

 in the drawing by dotted outlines, making twenty-seven as the 

 entire number. The teerh are very closely placed, almost 

 touching each other at their bases. They are smoothly and 

 gently convex on the outer side, from one and a half to more 

 than two times as long as wide. They are rather acute and 

 longer anteriorly ; more obtusely pointed posteriorly. They 

 are evidently inserted in a single row. 



Sixty-two described genera of American Permian or Permo- 

 Carboniferous amphibians and reptiles are at the present time 

 recognized as presumably valid. A few of these are yet 

 known only from incomplete or fragmentary material, and 

 will not be securely established until more is known of them. 

 About fifteen genera are now known from practically complete 

 skeletons. In the Chicago collections forty-four distinct genera 

 have been recognized, with two or three additional, more or 

 less doubtful, described ones. 



